In the sanitary paper converting industry, wide webs of lightweight tissue or toweling stock are rewound from large mill rolls into wide logs of about 4" to 6" diameter, which are then cut into individual consumer size rolls for subsequent packaging. Saws used for this cutting operation are well known and have single rotating blades mounted on pivoting or rotating arm assemblies as described in U.S. Pat. Nos. 2,752,999, 2,766,566, 3,213,731, 3,282,470, or can have two rotating blades as described in U.S. Pat. No. 4,041,813. A typical grinding assembly to keep the cutting blades sharp is described in '813 and in U.S. Pat. No. 4,347,771. Both patents are directed toward grinding stones which are not driven, but which rotate on urging contact with a driven rotating blade, however, either idling or driven grinder stones can be applied to the structure and concept of this invention.
Because of the abrasive nature of wood fibers and the density of the rewound logs, driven rotating blades must be sharpened frequently (for example every 5 to 15 seconds) to keep the blade edge honed, prevent bias cutting of the rolls, and maintain clean and square end cuts. Sharpening devices, including the grinding stones, stone drive system (if used), and associated actuating mechanisms, can be mounted differently. For example, the grinding "assembly" can be rigidly attached to a fixed frame and held in close proximity to the blade edge. When the pivoting or orbiting motion of the blade(s) is stopped, an actuating mechanism moves the grinding stones into contact with, and grinding operation for, the blades which are still rotatably driven, but which are temporarily stopped from orbiting motion. It will be recognized that when the blade orbit is stopped, cutting of logs cannot take place, and such stoppage for grinding represents lost production time.
Known prior art also involves saws where the grinding mechanisms are mounted in close proximity to and orbit with (or pivot with) the blades so that grinding can occur while the blade orbiting motion and cutting continues--this resulting in higher production since the saw blades continue in orbit while grinding occurs. It will be recognized that as blades are ground and honed, the diameter decreases. In prior art saws, periodic adjustments must be initiated to move the grinding assembly toward the center of blade rotation and, since the decreased blade diameter decreases the radius of the orbit, a further adjustment must be made to move the axis of orbiting motion such that the now decreased blade diameter (and the decreased orbit radius) are adjusted a like amount to ensure that the blade will still cut all the way through the log which is normally conveyed through the saw at a fixed elevation.